What's the weirdest sky you've ever seen before a storm moved in?

I'm not talking about the classic green wall or the shelf cloud everyone photographs. I mean the sky that made you pull over and just sit there, the one that felt wrong in a way you couldn't name. I've been chasing for years and I still can't explain what that pale yellow light was doing last June — I'm curious if other people have that one sky they still think about.